Lettuce variety 79-504 rz

ABSTRACT

The present invention relates to a  Lactuca sativa  seed designated 79-504 RZ, which may exhibit a combination of traits including resistance against downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII ( Bremia lactucae ), currant-lettuce aphid ( Nasonovia ribisnigri ) biotype Nr:0, and lettuce mosaic virus (LMV), as well as an extraordinary high number of substantially equally sized leaves, which leaves are medium green, slightly to moderately blistered, and have a slightly to moderately undulated apical leaf margin, which is shallowly dentate. The present invention also relates to a  Lactuca sativa  plant produced by growing the 79-504 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 79-504 RZ.

INCORPORATION BY REFERENCE

This application claims priority to U.S. provisional patent applicationSer. No. 61/896,330, filed Oct. 28, 2013.

The foregoing application, and all documents cited therein or duringtheir prosecution (“appln cited documents”) and all documents cited orreferenced in the appln cited documents, and all documents cited orreferenced herein (“herein cited documents”), and all documents cited orreferenced in herein cited documents, together with any manufacturer'sinstructions, descriptions, product specifications, and product sheetsfor any products mentioned herein or in any document incorporated byreference herein, are hereby incorporated herein by reference, and maybe employed in the practice of the invention. More specifically, allreferenced documents are incorporated by reference to the same extent asif each individual document was specifically and individually indicatedto be incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a new lettuce (Lactuca sativa) varietywhich may exhibit a combination of traits including resistance againstdowny mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

BACKGROUND OF THE INVENTION

All cultivated forms of lettuce belong to the highly polymorphicspecies, Lactuca sativa, which is grown for its edible head and leaves.As a crop, lettuces are grown commercially wherever environmentalconditions permit the production of an economically viable yield.

Lactuca sativa is in the Cichoreae tribe of the Asteraceae (Compositae)family. Lettuce is related to chicory, sunflower, aster, scorzonera,dandelion, artichoke and chrysanthemum. Sativa is one of about 300species in the genus Lactuca.

Lettuce cultivars are susceptible to a number of pests and diseases suchas downy mildew (Bremia lactucae). Every year this disease leads tomillions of dollars of lost lettuce crop throughout the world. Downymildew (Bremia lactucae) is highly destructive on lettuce grown atrelatively low temperature and high humidity. Downy mildew is caused bya fungus, Bremia lactucae, which can be one of the following strains:NL1, NL2, NL4, NL5, NL6, NL7, NL10, NL12, NL13, NL14, NL15, NL16, Bl:17,Bl:18, Bl:20, Bl:21, Bl:22, Bl:23, Bl:24, Bl:25, Bl:26, Bl:27, Bl:28,Bl:29, Bl:30, Bl:31 (Van Ettekoven, K. et al., “Identification anddenomination of ‘new’ races of Bremia lactucae,” In: Lebeda, A. andKristkova, E (eds.), Eucarpia Leafy Vegetables, 1999, PalackyUniversity, Olomouc, Czech Republic, pp. 171-175; Van der Arend et al.“Identification and denomination of “new” races of Bremia lactucae inEurope by IBEB until 2002.” In: Van Hintum, Th et al. (eds.), EucarpiaLeafy Vegetables Conference 2003, Centre for Genetic Resources,Wageningen, The Netherlands, p. 151; Plantum NL (Dutch association forbreeding, tissue culture, production and trade of seeds and youngplants), Van der Arend et al. “Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2002.” In: Van Hintum,Th et al. (eds.), Eucarpia Leafy Vegetables Conference 2003, Centre forGenetic Resources, Wageningen, The Netherlands, p. 151; Plantum NL(Dutch association for breeding, tissue culture, production and trade ofseeds and young plants); IBEB press release “New race of Bremia lactucaeBl:27 identified and nominated”, May 2010; Plantum NL (Dutch associationfor breeding, tissue culture, production and trade of seeds and youngplants), “New race of Bremia lactucae Bl:28 identified and nominated”,March 2011; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New races of Bremia lactucae, Bl:29, Bl:30 and Bl:31 identified andnominated”, August 2013), Ca-I, Ca-IIA, Ca-IIB, Ca-III, Ca-IV(Schettini, T. M., Legg, E. J., Michelmore, R. W., 1991. Insensitivityto metalaxyl in California populations of Bremia lactucae and resistanceof California lettuce cultivars to downy mildew. Phytopathology 81(1).p. 64-70), and Ca-V, Ca-VI, Ca-VII, Ca-VIII (Michelmore R. & Ochoa. O.“Breeding Crisphead Lettuce.” In: California Lettuce Research Board,Annual Report 2005-2006, 2006, Salinas, California, pp. 55-68).

Downy mildew causes pale, angular, yellow areas bounded by veins on theupper leaf surfaces. Sporulation occurs on the opposite surface of theleaves. The lesions eventually turn brown, and they may enlarge andcoalesce. These symptoms typically occur first on the lower leaves ofthe lettuce, but under ideal conditions may move into the upper leavesof the head. When the fungus progresses to this degree, the head cannotbe harvested. Less severe damage requires the removal of more leavesthan usual, especially when the lettuce reaches its final destination.

Of the various species of aphids that feed on lettuce, thecurrant-lettuce aphid (Nasonovia ribisnigri) is the most destructivespecies because it feeds both on the leaves of the lettuce as well asthe heart of the lettuce, making it difficult to control withconventional insecticides. The lettuce aphid feeds by sucking sap fromthe lettuce leaves. Although direct damage to the lettuce may belimited, its infestation has serious consequences because the presenceof aphids makes lettuce unacceptable to consumers.

Lettuce mosaic virus (LMV) mainly infects lettuce seeds, which is theprimary way that the virus is introduced to lettuce in the fields, butalso can infect numerous crops and weeds, thereby creating reservoirs ofthe virus. LMV also can be vectored by aphids, which spread the viruswithin a lettuce field and introduce it into lettuce fields frominfected weeds and crops outside the field.

Symptoms of LMV vary greatly. Leaves of plants that are infected at ayoung stage are stunted, deformed and (in some varieties) show a mosaicor mottling pattern. Such plants rarely grow to full size; head lettucevarieties infected early fail to form heads. Plants that are infectedlater in the growth cycle show a different set of symptoms. These plantsmay reach full size, but the older outer leaves turn yellow, twisted,and otherwise are deformed. On head lettuce, the wrapper leaves oftenwill curve back away from the head and developing heads may be deformed.In some cases, brown necrotic flecks occur on the wrapper leaves.

Although several known lettuce cultivars exhibit resistance againstdowny mildew, irrespective of lettuce type, all the lettuce cultivarsaffected produce a limited number of leaves that generally are ofunequal size and diminished quality with respect to color and shape.This is a distinct disadvantage for processing purposes because leaveseither need to be sorted based on size or they need to be cut to asmaller, more uniform size. The first option requires additional labor,with not all sizes usable. The second option has the disadvantage thatit creates many cut surfaces, which then are subject to wound-inducedbrowning, resulting in a greatly reduced shelf-life.

Another important requirement for processed lettuce leaves sold aspre-packed lettuces which is already cut and washed, is a non-flat leafshape. Non-flat leaves stick less to the plastic film and fill up thebag more easily. This makes the bag more attractive for consumers buyingpre-packed lettuce. Non-flat leaves are characterized as mature leaveshaving a combination of slight to moderate blistering and slight tomoderate undulations of the apical leaf margin, which is shallowlydentate.

Citation or identification of any document in this application is not anadmission that such document is available as prior art to the presentinvention.

SUMMARY OF THE INVENTION

There exists a need, therefore, for a lettuce variety which exhibits acombination of traits including resistance against downy mildew strainsBl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate.

The present invention addresses this need by providing a new type oflettuce (Lactuca sativa) variety, designated 79-504 RZ. Lettuce cultivar79-504 RZ exhibits a combination traits including resistance againstdowny mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

The present invention provides seeds of lettuce cultivar 79-504 RZ,which have been deposited with the National Collections of Industrial,Marine and Food Bacteria (NCIMB) in Bucksburn, Aberdeen AB21 9YA,Scotland, UK and have been assigned NCIMB Accession No. 42166.

In one embodiment, the invention provides a lettuce plant designated79-504 RZ, representative seed of which have been deposited under NCIMBAccession No. 42166, wherein said lettuce plant may comprise acombination of traits including resistance against downy mildew strainsBl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate.

In one embodiment, the invention provides a lettuce plant designated79-504 RZ which may exhibit a combination of traits including resistanceagainst downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremialactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,and lettuce mosaic virus (LMV), as well as an extraordinary high numberof substantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate and wherein theplant is very slow bolting, representative seed of which have beendeposited under NCIMB Accession No. 42166.

In one embodiment, the invention provides a lettuce plant designated79-504 RZ, representative seed of which have been deposited under NCIMBAccession No. 42166.

In an embodiment of the present invention, there also is provided partsof a lettuce plant of the invention, which may include parts of alettuce plant exhibiting a combination of traits including resistanceagainst downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremialactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,and lettuce mosaic virus (LMV), as well as an extraordinary high numberof substantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate, or parts of alettuce plant having any of the aforementioned resistance(s) and acombination of traits including one or more morphological orphysiological characteristics tabulated herein, including parts oflettuce variety 79-504 RZ, wherein the plant parts are involved insexual reproduction, which include, without limitation, microspores,pollen, ovaries, ovules, embryo sacs or egg cells and/or wherein theplant parts are suitable for vegetative reproduction, which include,without limitation, cuttings, roots, stems, cells or protoplasts and/orwherein the plant parts are tissue culture of regenerable cells in whichthe cells or protoplasts of the tissue culture are derived from a tissuesuch as, for example and without limitation, leaves, pollen, embryos,cotyledon, hypocotyls, meristematic cells, roots, root tips, anthers,flowers, seeds or stems. The plants of the invention from which suchparts may come from include those wherein representative seed of whichhas been deposited under NCIMB Accession No. 42166 or lettuce variety orcultivar designated 79-504 RZ, as well as seed from such a plant, plantparts of such a plant (such as those mentioned herein) and plants fromsuch seed and/or progeny of such a plant, advantageously progenyexhibiting such combination of such traits, each of which, is within thescope of the invention; and such combination of traits.

In another embodiment there is a plant grown from seeds, representativeseed of which having been deposited under NCIMB Accession No. 42166.

In a further embodiment there is a plant regenerated from theabove-described plant parts or regenerated from the above-describedtissue culture. Advantageously such a plant may have morphologicaland/or physiological characteristics of lettuce variety 79-504 RZ and/orof a plant grown from seed, representative seed of which having beendeposited under NCIMB Accession No. NCIMB 42166—including withoutlimitation such plants having all of the morphological and physiologicalcharacteristics of lettuce variety 79-504 RZ and/or of plant grown fromseed, representative seed of which having been deposited under NCIMBAccession No. NCIMB 42166. Advantageously, such a plant demonstrates thetraits of resistance against downy mildew strains Bl:1 to Bl:31, CA-I toCA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, and lettuce mosaic virus (LMV), as well as anextraordinary high number of substantially equally sized leaves, whichleaves are medium green, slightly to moderately blistered, and have aslightly to moderately undulated apical leaf margin, which is shallowlydentate.

Accordingly, in still a further embodiment, there is provided a lettuceplant having all of the morphological and physiological characteristicsof lettuce variety 79-504 RZ, representative seed of which having beendeposited under NCIMB Accession No. 42166. Such a plant may be grownfrom the seeds, regenerated from the above-described plant parts, orregenerated from the above-described tissue culture. A lettuce planthaving any of the aforementioned resistance(s), and one or moremorphological or physiological characteristics recited or tabulatedherein, and a lettuce plant advantageously having all of theaforementioned resistances and the characteristics recited and tabulatedherein, are preferred. Parts of such plants—such as those plant partsabove-mentioned—are encompassed by the invention.

In one embodiment, there is provided a method for producing a progeny oflettuce cultivar 79-504 RZ which may comprise crossing the a plantdesignated 79-504 RZ with itself or with another lettuce plant,harvesting the resultant seed, and growing said seed.

In a further embodiment there is provided a progeny plant produced bysexual or vegetative reproduction, grown from seeds, regenerated fromthe above-described plant parts, or regenerated from the above-describedtissue culture of the lettuce cultivar or a progeny plant thereof,representative seed of which having been deposited under NCIMB AccessionNo. 42166. The progeny may have any of the aforementioned resistance(s),and one or more morphological or physiological characteristics recitedor tabulated herein, and a progeny plant advantageously having all ofthe aforementioned resistances and the characteristics recited andtabulated herein, are preferred. Advantageously, the progeny demonstratethe traits of resistance against downy mildew strains Bl:1 to Bl:31,CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonoviaribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), as well as anextraordinary high number of substantially equally sized leaves, whichleaves are medium green, slightly to moderately blistered, and have aslightly to moderately undulated apical leaf margin, which is shallowlydentate.

Progeny of the lettuce variety 79-504 RZ may be modified in one or moreother characteristics, in which the modification is a result of, forexample and without limitation, mutagenesis or transformation with atransgene.

In still another embodiment, the present invention provides progeny oflettuce cultivar 79-504 RZ produced by sexual or vegetativereproduction, grown from seeds, regenerated from the above-describedplant parts, or regenerated from the above-described tissue culture ofthe lettuce cultivar or a progeny plant thereof, in which theregenerated plant shows a combination of traits including resistanceagainst downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremialactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,and lettuce mosaic virus (LMV), as well as an extraordinary high numberof substantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

In still a further embodiment, the invention provides a method ofproducing a hybrid lettuce seed which may comprise crossing a firstparent lettuce plant with a second parent lettuce plant and harvestingthe resultant hybrid lettuce seed, in which the first parent lettuceplant or the second parent lettuce plant may be a lettuce plant of theinvention, e.g. a lettuce plant having a combination of traits includingresistance against downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII(Bremia lactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotypeNr:0, and lettuce mosaic virus (LMV), as well as an extraordinary highnumber of substantially equally sized leaves, which leaves are mediumgreen, slightly to moderately blistered, and have a slightly tomoderately undulated apical leaf margin, which is shallowly dentate andone or more morphological or physiological characteristics tabulatedherein, including a lettuce plant of lettuce cultivar 79-504 RZ,representative seed of which having been deposited under NCIMB 42166.

In another embodiment, the invention provides producing a lettuce plantwhich may exhibit a combination of traits including resistance againstdowny mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate which maycomprise: crossing a mother lettuce plant with a father lettuce plant toproduce a hybrid seed; growing said hybrid seed to produce a hybridplant; selfing said hybrid plant to produce F2 progeny seed; growingsaid F2 progeny seed to produce F2-plants; selecting said F2-plants forexhibiting a combination of traits including resistance against downymildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

Advantageously the selfing and selection may be repeated; for example atleast once, or at least twice, thrice, four times, five times, six timesor more, to produce F3 or F4 or F5 or F6 or subsequent progeny,especially as progeny from F2 may exhibit the aforementioned combinationof traits, and may be desirable.

In still a further embodiment, the invention provides a method ofproducing a lettuce cultivar which may exhibit a combination of traitsincluding resistance against downy mildew strains Bl:1 to Bl:31, CA-I toCA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonovia ribisnigri)biotype Nr:0, and lettuce mosaic virus (LMV), as well as anextraordinary high number of substantially equally sized leaves, whichleaves are medium green, slightly to moderately blistered, and have aslightly to moderately undulated apical leaf margin, which is shallowlydentate.

The invention even further relates to a method of producing lettucewhich may comprise: (a) cultivating to the vegetative plant stage aplant of lettuce variety 79-504 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. NCIMB 42166, and (b) harvestinglettuce leaves or heads from the plant. The invention furthercomprehends packaging and/or processing the lettuce plants, heads orleaves.

Accordingly, it is an object of the invention to not encompass withinthe invention any previously known product, process of making theproduct, or method of using the product such that Applicants reserve theright and hereby disclose a disclaimer of any previously known product,process, or method. It is further noted that the invention does notintend to encompass within the scope of the invention any product,process, or making of the product or method of using the product, whichdoes not meet the written description and enablement requirements of theUSPTO (35 U.S.C. §112, first paragraph) or the EPO (Article 83 of theEPC), such that Applicants reserve the right and hereby disclose adisclaimer of any previously described product, process of making theproduct, or method of using the product.

It is noted that in this disclosure and particularly in the claims,terms such as “comprises”, “comprised”, and “comprising” and the like(e.g., “includes”, “included”, “including”, “contains”, “contained”,“containing”, “has”, “had”, “having”, etc.) can have the meaningascribed to them in US Patent law, i.e., they are open ended terms. Forexample, any method that “comprises,” “has” or “includes” one or moresteps is not limited to possessing only those one or more steps and alsocovers other unlisted steps. Similarly, any plant that “comprises,”“has” or “includes” one or more traits is not limited to possessing onlythose one or more traits and covers other unlisted traits. Similarly,the terms “consists essentially of” and “consisting essentially of” havethe meaning ascribed to them in US Patent law, e.g., they allow forelements not explicitly recited, but exclude elements that are found inthe prior art or that affect a basic or novel characteristic of theinvention. See also MPEP §2111.03. In addition, the term “about” is usedto indicate that a value includes the standard deviation of error forthe device or method being employed to determine the value.

These and other embodiments are disclosed or are obvious from andencompassed by the following Detailed Description.

DEPOSIT

The Deposit with NCIMB Ltd, Ferguson Building, Craibstone Estate,Bucksburn, Aberdeen AB21 9YA, UK, on Oct. 10, 2013, under depositaccession number NCIMB 42166 was made pursuant to the terms of theBudapest Treaty. Upon issuance of a patent, all restrictions upon thedeposit will be removed, and the deposit is intended to meet therequirements of 37 CFR §1.801-1.809. The deposit will be maintained inthe depository for a period of 30 years, or 5 years after the lastrequest, or for the effective life of the patent, whichever is longer,and will be replaced if necessary during that period.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but notintended to limit the invention solely to the specific embodimentsdescribed, may best be understood in conjunction with the accompanyingdrawing, in which:

FIG. 1 is an illustration of six different shapes of the fourth leaffrom a 20-day old seedling grown under optimal conditions.

FIG. 2 is a picture of the shape of the fourth leaf of 79-504 RZ.

FIG. 3 is a picture of the shape of a mature leaf of 79-504 RZ.

FIG. 4 is a picture of the shape of the fourth leaf of comparisonvariety Emerson.

FIG. 5 is a picture of the shape of a mature leaf of comparison varietyEmerson.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides methods and compositions relating to plants,seeds and derivatives of a new lettuce variety herein referred to aslettuce variety 79-504 RZ. Lettuce variety 79-504 RZ is a uniform andstable line, distinct from other such lines.

In a preferred embodiment, the specific type of breeding method employedfor developing a lettuce cultivar is pedigree selection, where bothsingle plant selection and mass selection practices are employed.Pedigree selection, also known as the “Vilmorin system of selection,” isdescribed in Fehr, W., Principles of Cultivar Development, Volume I,MacMillan Publishing Co., which is hereby incorporated by reference.

When pedigree selection is applied, in general selection is firstpracticed among F₂ plants. In the next season, the most desirable F₃lines are first identified, and then desirable F₃ plants within eachline are selected. The following season and in all subsequentgenerations of inbreeding, the most desirable families are identifiedfirst, then desirable lines within the selected families are chosen, andfinally desirable plants within selected lines are harvestedindividually. A family refers to lines that were derived from plantsselected from the same progeny from the preceding generation.

Using this pedigree method, two parents may be crossed using anemasculated female and a pollen donor (male) to produce F₁ offspring.Lettuce is an obligate self-pollination species, which means that pollenis shed before stigma emergence, assuring 100% self-fertilization.Therefore, in order to optimize crossing, a method of misting may beused to wash the pollen off prior to fertilization to assure crossing orhybridization.

Parental varieties are selected from commercial varieties thatindividually exhibit one or more desired phenotypes. Additionally, anybreeding method involving selection of plants for the desired phenotypemay be used in the method of the present invention.

The F₁ may be self-pollinated to produce a segregating F₂ generation.Individual plants may then be selected which represent the desiredphenotype in each generation (F₃, F₄, F₅, etc.) until the traits arehomozygous or fixed within a breeding population.

The development of lettuce variety 79-504 RZ is described in Table 1.The seedlot in year 5, seed lot 12R.3150, was deposited at the NCIMBunder accession number NCIMB 42166.

In Table 1a detailed description of the development of Lettuce variety79-504 RZ is shown.

TABLE 1 Year Description Location 0 Final F1-cross plants Aramon,07A.28294 × 07A.28334 in France glasshouse. 1 F1 plant grown for F2 seedFijnaart, the production. Netherlands 2 F2 plant 09P.31689 selectedFijnaart, the in open field, followed by F3 Netherlands seed 10P.441091.3 F3 plant 10P.30760 selected Fijnaart, the in open field, followed byF4 Netherlands seed 11P.400015. 4 F4 plant 11P.30614 selected Fijnaart,the in open field, followed by F5 Netherlands seed 11P.404265. 5 F5 line12R.993150 Hoek van established uniform, Holland, multiplied inglasshouse: The seed lot 12R.3150 Netherlands

In one embodiment, a plant of the invention has all the morphologicaland physiological characteristics of lettuce variety 79-504 RZ. Thesecharacteristics of a lettuce plant of the invention, e.g. variety 79-504RZ, are summarized in Tables 2, 3 and 4.

Next to the morphological and physiological characteristics mentioned inTables 2, 3 and 4, a plant of the invention may also exhibit resistanceto downy mildew (Bremia lactucae Regel.).

As used herein resistance against Bremia lactucae is defined as theability of a plant to resist infection by each of the various strainsBl:1 to Bl:31, Ca-I to Ca-VIII of Bremia lactucae Regel. in all stagesbetween the seedling stage and the harvestable plant stage. Bl:1 toBl:31 means strains NL1, NL2, NL4, NL5, NL6, NL7, NL10, NL12, NL13,NL14, NL15, NL16, Bl:17, Bl:18, Bl:20, Bl:21, Bl:22, Bl:23, Bl:24,Bl:25, Bl:26, Bl:27, Bl:28, Bl:29, Bl:30, Bl:31 (Van Ettekoven K, Vander Arend A J M, 1999. identification and denomination of ‘new’ races ofBremia lactucae. In: Lebeda A, Kristkova E (eds.) Eucarpia leafyvegetables '99. Palacky University, Olomouc, Czech Republic, 1999:171-175; Van der Arend, A. J. M., Gautier, J., Guenard, M., Michel, H.,Moreau, B., de Ruijter, J., Schut, J. W. and de Witte, I. (2003).Identification and denomination of ‘new’ races of Bremia lactucae inEurope by IBEB until 2002. In: Eucarpia leafy vegetables 2003.Proceedings of the Eucarpia Meeting on leafy vegetables genetics andbreeding. Noorwijkerhout, The Netherlands. Eds. Van Hintum T., LebedaA., Pink D., Schut J. pp 151-160; Van der Arend A J M, Gautier J,Grimault V, Kraan P, Van der Laan R, Mazet J, Michel H, Schut J W,Smilde D, De Witte I (2006) Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2006; incorporatedherein by reference; Plantum NL (Dutch association for breeding, tissueculture, production and trade of seeds and young plants), IBEB pressrelease, “New race of Bremia lactucae Bl:27 identified and nominated”,May 2010; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New race of Bremia lactucae Bl:28 identified and nominated”, March2011; Plantum NL (Dutch association for breeding, tissue culture,production and trade of seeds and young plants), IBEB press release,“New races of Bremia lactucae, Bl:29, Bl:30 and Bl:31 identified andnominated”, August 2013). Ca-I to Ca-VIII means Ca-I, Ca-IIA, Ca-IIB,Ca-III, Ca-IV (Schettini, T. M., Legg, E. J., Michelmore, R. W., 1991.Insensitivity to metalaxyl in California populations of Bremia lactucaeand resistance of California lettuce cultivars to downy mildew,Phytopathology 81(1). p. 64-70), and Ca-V, Ca-VI, Ca-VII, Ca-VIII(Michelmore R. & Ochoa. O. “Breeding Crisphead Lettuce.” In: CaliforniaLettuce Research Board, Annual Report 2005-2006, 2006, Salinas,California, pp. 55-68).

Resistance typically is tested by two interchangeable methods, describedby Bonnier, F. J. M. et al. (Euphytica, 61(3):203-211, 1992;incorporated herein by reference). One method involves inoculating 7-dayold seedlings, and observing sporulation 10 to 14 days later. The othermethod involves inoculating leaf discs with a diameter of 18 mm obtainedfrom a non-senescent, fully grown true leaf and observing sporulation 10days later.

As used herein, resistance against Nasonovia ribisnigri (Mosley), orcurrant-lettuce aphid, is defined as the plant characteristic whichresults in a non-feeding response of the aphid on the leaves of theplant in all stages between 5 true-leaf stage and harvestable plantstage (U.S. Pat. No. 5,977,443 to Jansen, J. P. A., “Aphid Resistance inComposites,” p. 12, 1999; incorporated herein by reference).

Resistance is tested by spreading at least ten aphids of biotype Nr:0 ona plant in a plant stage between 5 true leaves and harvestable stage,and observing the density of the aphid population on the plant as wellas the growth reduction after 14 days in a greenhouse, with temperaturesettings of 23 degrees Celsius in daytime and 21 degrees Celsius atnight. Day length is kept at 18 hours by assimilation lights.

As used herein, resistance against lettuce mosaic virus (LMV) may bedefined as the ability of the plant to grow normally after LMV infectionand to inhibit the virus transmission to seed. Resistance may be testedby mechanical inoculation of young plants in a climate cell orgreenhouse, as described by Pink, D. A. C. et al. (Plant Pathology,41(1): 5-12, 1992), incorporated herein by reference. Inoculatedresistant plants grow just as well as uninoculated plants and show nochlorosis or mosaic symptoms. The LMV isolate, which may be used fortesting, is Ls-1 (International Union for the Protection of NewVarieties of Plants [UPOV], Guidelines for the conduct of tests fordistinctness, uniformity and stability; lettuce (Lactuca sativa L.),2002, p. 35; incorporated herein by reference).

As used herein, an extraordinary high leaf number is the leaf number ofa lettuce plant which is at least about two times to about four times ashigh as the leaf number of a plant of a regular lettuce variety grown inthe same environment during the same period of time. The observation ofleaf number should be done at the plant stage where the above-ground drymatter is between 100 and 400 grams and before the plant starts to bolt.

As used herein, a multileaf lettuce plant is a lettuce plant with anextraordinary high leaf number. This is caused by a single recessivegenetic factor, which is present in the plant in a homozygous state.

As used herein, a medium green fourth leaf, is a fourth leaf with acolor that has the same color as the variety Emerson.

As used herein, slight to moderate blistering of mature leaves, is adegree of blistering that is stronger than the variety Pascal.

As used herein, slight to moderate undulations of the apical leafmargin, is a degree of undulation that is clearly visible and thusstronger than the variety Socrates grown under long-day outdoorconditions at a latitude of 52°, i.e. sowing 100 days before the longestday, in an Oceanic climate (Koppen-classification: Cfb; McKnight & Hess,2000. Physical Geography: A Landscape Appreciation. Upper Saddle River,N.J.: Prentice Hall).

As used herein, a shallowly dentate margin of a mature leaf, is a leafmargin which has a clearly visible and thus stronger indentation thanthe variety Socrates grown under long-day outdoor conditions at alatitude of 52°, i.e. sowing 100 days before the longest day, in anOceanic climate (Koppen-classification: Cfb; McKnight & Hess, 2000.Physical Geography: A Landscape Appreciation. Upper Saddle River, N.J.:Prentice Hall).

Embodiments of the inventions advantageously have one or more, and mostadvantageously all, of these characteristics.

In Table 2, the seed color, cotyledon shape and characteristics of thefourth leaf of “79-504 RZ” is compared with “Emerson” and “GrandRapids”.

TABLE 2 Character 79-504 RZ Emerson Grand Rapids Plant Type Cutting leafCutting leaf Cutting leaf Seed Color Black (grey, Black (grey, Black(grey, brown) brown) brown) Cotyledon Shape Intermediate IntermediateIntermediate to broad Shape of Fourth Elongated Elongated Elongated LeafRolling of Fourth Present Present Present Leaf Cupping of FourthUncupped Uncupped Uncupped Leaf Fourth Leaf Apical Coarsely EntireEntire Margin dentate Fourth Leaf Basal Coarsely Coarsely CoarselyMargin dentate dentate dentate Undulation Slight Flat Slight to mediumGreen color Medium Medium Yellow green green green Anthocyanin AbsentAbsent Absent distribution

In Table 3, the mature leaf and head characteristics of “79-504 RZ” iscompared with “Emerson” and “Grand Rapids”. RHS=Royal HorticuluralSociety colour chart code.

TABLE 3 Character 79-504 RZ Emerson Grand Rapids Leaf Color mediummedium yellowish green green light green Anthocyanin Absent AbsentAbsent Distribution Margin Incision Absent/ Absent/ Absent/ Depthshallow shallow shallow Margin Shallowly Entire Shallowly Indentationdentate dentate Undulations Moderate to Absent Moderate of the Apicalslight Margin Leaf Size Small Small Medium Leaf Glossiness Dull to DullModerate moderate Leaf Blistering slight to Absent Strong moderate LeafThickness Thin Thin Intermediate to thin Trichomes Absent Absent AbsentHead Shape Non- Non- Non- heading heading heading Butt Shape Flat toFlat to Rounded slightly slightly concave concave Midrib ModeratelyModerately Moderately raised raised raised Bolting class Very slowMedium Medium Number of days 153 113 112 from first water to seed stalkBolter leaves Curved Straight Curved

In Table 4, The main characteristics of “79-504 RZ” are compared with“Emerson (79-11 RZ)”, “Aquino (79-176 RZ)”, “Pascal (79-110 RZ)”, and“Socrates (79-22 RZ)”.

TABLE 4 Aquino Pascal Socrates 79-504 (79-176 Emerson (79-110 (79-22Character RZ RZ) (79-11 RZ) RZ) RZ) Resistance B1:1-31 B1:1-31 B1:1-31B1:1-31 B1:1-17, to Bremia & CA-I & CA-I to & CA-I to & CA-I to 21, 23 &lactucae to CA-VIII CA-VIII CA-VIII CA-I to race: CA-VIII CA-VIIIResistance Resistant Resistant Susceptible Resistant Susceptible toNasonovia ribisnigri biotype Nr: 0 Resistance Resistant SusceptibleSusceptible Susceptible Susceptible to LMV Fourth leaf: Medium MediumMedium Dark green Medium green color green green green green Matureleaf: Slight to Absent Absent Absent/ Absent blistering moderate slightMature leaf: Slight to Absent Absent Absent Absent degree of moderateundulation of apical leaf margin Mature leaf: Shallowly Entire EntireEntire Entire indentation dentate of leaf margin

In an embodiment, the invention relates to lettuce plants that has allthe morphological and physiological characteristics of the invention andhave acquired said characteristics by introduction of the geneticinformation that is responsible for the characteristics from a suitablesource, either by conventional breeding, or genetic modification, inparticular by cisgenesis or transgenesis. Cisgenesis is geneticmodification of plants with a natural gene, coding for an (agricultural)trait, from the crop plant itself or from a sexually compatible donorplant. Transgenesis is genetic modification of a plant with a gene froma non-crossable species or a synthetic gene.

Just as useful traits that may be introduced by backcrossing, usefultraits may be introduced directly into the plant of the invention, beinga plant of lettuce variety 79-504 RZ, by genetic transformationtechniques; and, such plants of lettuce variety 79-504 RZ that haveadditional genetic information introduced into the genome or thatexpress additional traits by having the DNA coding there for introducedinto the genome via transformation techniques, are within the ambit ofthe invention, as well as uses of such plants, and the making of suchplants.

Genetic transformation may therefore be used to insert a selectedtransgene into the plant of the invention, being a plant of lettucevariety 79-504 RZ or may, alternatively, be used for the preparation oftransgenes which may be introduced by backcrossing. Methods for thetransformation of plants, including lettuce, are well known to those ofskill in the art.

Vectors used for the transformation of lettuce cells are not limited solong as the vector may express an inserted DNA in the cells. Forexample, vectors which may comprise promoters for constitutive geneexpression in lettuce cells (e.g., cauliflower mosaic virus 35Spromoter) and promoters inducible by exogenous stimuli may be used.Examples of suitable vectors include pBI binary vector. The “lettucecell” into which the vector is to be introduced includes various formsof lettuce cells, such as cultured cell suspensions, protoplasts, leafsections, and callus. A vector may be introduced into lettuce cells byknown methods, such as the polyethylene glycol method, polycationmethod, electroporation, Agrobacterium-mediated transfer, particlebombardment and direct DNA uptake by protoplasts. To effecttransformation by electroporation, one may employ either friabletissues, such as a suspension culture of cells or embryogenic callus oralternatively one may transform immature embryos or other organizedtissue directly. In this technique, one would partially degrade the cellwalls of the chosen cells by exposing them to pectin-degrading enzymes(pectolyases) or mechanically wound tissues in a controlled manner.

A particularly efficient method for delivering transforming DNA segmentsto plant cells is microprojectile bombardment. In this method, particlesare coated with nucleic acids and delivered into cells by a propellingforce. Exemplary particles include those which may be comprised oftungsten, platinum, and preferably, gold. For the bombardment, cells insuspension are concentrated on filters or solid culture medium.Alternatively, immature embryos or other target cells may be arranged onsolid culture medium. The cells to be bombarded are positioned at anappropriate distance below the macroprojectile stopping plate. Anillustrative embodiment of a method for delivering DNA into plant cellsby acceleration is the Biolistics Particle Delivery System, which may beused to propel particles coated with DNA or cells through a screen, suchas a stainless steel or Nytex screen, onto a surface covered with targetlettuce cells. The screen disperses the particles so that they are notdelivered to the recipient cells in large aggregates. It is believedthat a screen intervening between the projectile apparatus and the cellsto be bombarded reduces the size of projectiles aggregate and maycontribute to a higher frequency of transformation by reducing thedamage inflicted on the recipient cells by projectiles that are toolarge. Microprojectile bombardment techniques are widely applicable, andmay be used to transform virtually any plant species, including a plantof lettuce variety 79-504 RZ.

Agrobacterium-mediated transfer is another widely applicable system forintroducing gene loci into plant cells. An advantage of the technique isthat DNA may be introduced into whole plant tissues, thereby bypassingthe need for regeneration of an intact plant from a protoplast.Agrobacterium transformation vectors are capable of replication in E.coli as well as Agrobacterium, allowing for convenient manipulations.Moreover, advances in vectors for Agrobacterium-mediated gene transferhave improved the arrangement of genes and restriction sites in thevectors to facilitate the construction of vectors capable of expressingvarious polypeptide coding genes. The vectors have convenientmulti-linker regions flanked by a promoter and a polyadenylation sitefor direct expression of inserted polypeptide coding genes.Additionally, Agrobacterium containing both armed and disarmed Ti genesmay be used for transformation. In those plant strains whereAgrobacterium-mediated transformation is efficient, it is the method ofchoice because of the facile and defined nature of the gene locustransfer. The use of Agrobacterium-mediated plant integrating vectors tointroduce DNA into plant cells, including lettuce plant cells, is wellknown in the art (See, e.g., U.S. Pats. No. 7,250,560 and 5,563,055).

Transformation of plant protoplasts also may be achieved using methodsbased on calcium phosphate precipitation, polyethylene glycol treatment,electroporation, and combinations of these treatments.

A number of promoters have utility for plant gene expression for anygene of interest including but not limited to selectable markers,scoreable markers, genes for pest tolerance, disease resistance,nutritional enhancements and any other gene of agronomic interest.Examples of constitutive promoters useful for lettuce plant geneexpression include, but are not limited to, the cauliflower mosaic virus(CaMV) P-35S promoter, a tandemly duplicated version of the CaMV 35Spromoter, the enhanced 35S promoter (P-e35S), the nopaline synthasepromoter, the octopine synthase promoter, the figwort mosaic virus(P-FMV) promoter (see U.S. Pat. No. 5,378,619), an enhanced version ofthe FMV promoter (P-eFMV) where the promoter sequence of P-FMV isduplicated in tandem, the cauliflower mosaic virus 19S promoter, asugarcane bacilliform virus promoter, a commelina yellow mottle viruspromoter, the promoter for the thylakoid membrane proteins from lettuce(psaD, psaF, psaE, PC, FNR, atpC, atpD, cab, rbcS) (see U.S. Pat. No.7,161,061), the CAB-1 promoter from lettuce (see U.S. Pat. No.7,663,027), the promoter from maize prolamin seed storage protein (seeU.S. Pat. No. 7,119,255), and other plant DNA virus promoters known toexpress in plant cells. A variety of plant gene promoters that areregulated in response to environmental, hormonal, chemical, and/ordevelopmental signals may be used for expression of an operably linkedgene in plant cells, including promoters regulated by (1) heat, (2)light (e.g., pea rbcS-3A promoter, maize rbcS promoter, or chlorophylla/b-binding protein promoter), (3) hormones, such as abscisic acid, (4)wounding (e.g., wunl, or (5) chemicals such as methyl jasmonate,salicylic acid, or Safener. It may also be advantageous to employorgan-specific promoters.

Exemplary nucleic acids which may be introduced to the lettuce varietyof this invention include, for example, DNA sequences or genes fromanother species, or even genes or sequences which originate with or arepresent in lettuce species, but are incorporated into recipient cells bygenetic engineering methods rather than classical reproduction orbreeding techniques. However, the term “exogenous” is also intended torefer to genes that are not normally present in the cell beingtransformed, or perhaps simply not present in the form, structure, etc.,as found in the transforming DNA segment or gene, or genes which arenormally present and that one desires to express in a manner thatdiffers from the natural expression pattern, e.g., to over-express.Thus, the term “exogenous” gene or DNA is intended to refer to any geneor DNA segment that is introduced into a recipient cell, regardless ofwhether a similar gene may already be present in such a cell. The typeof DNA included in the exogenous DNA may include DNA which is alreadypresent in the plant cell, DNA from another plant, DNA from a differentorganism, or a DNA generated externally, such as a DNA sequencecontaining an antisense message of a gene, or a DNA sequence encoding asynthetic or modified version of a gene.

Many hundreds if not thousands of different genes are known and couldpotentially be introduced into a plant of lettuce variety 79-504 RZ.Non-limiting examples of particular genes and corresponding phenotypesone may choose to introduce into a lettuce plant include one or moregenes for insect tolerance, pest tolerance such as genes for fungaldisease control, herbicide tolerance, and genes for quality improvementssuch as yield, nutritional enhancements, environmental or stresstolerances, or any desirable changes in plant physiology, growth,development, morphology or plant product(s).

Alternatively, the DNA coding sequences may affect these phenotypes byencoding a non-translatable RNA molecule that causes the targetedinhibition of expression of an endogenous gene, for example viaantisense- or cosuppression-mediated mechanisms. The RNA could also be acatalytic RNA molecule (i.e., a ribozyme) engineered to cleave a desiredendogenous mRNA product. Thus, any gene which produces a protein or mRNAwhich expresses a phenotype or morphology change of interest is usefulfor the practice of the present invention. (See also U.S. Pat. No.7,576,262, “Modified gene-silencing RNA and uses thereof.”)

U.S. Pats. Nos. 7,230,158, 7,122,720, 7,081,363, 6,734,341, 6,503,732,6,392,121, 6,087,560, 5,981,181, 5,977,060, 5,608,146, 5,516,667, eachof which, and all documents cited therein are hereby incorporated hereinby reference, consistent with the above INCORPORATION BY REFERENCEsection, are additionally cited as examples of U.S. patents that mayconcern transformed lettuce and/or methods of transforming lettuce orlettuce plant cells, and techniques from these US patents, as well aspromoters, vectors, etc., may be employed in the practice of thisinvention to introduce exogenous nucleic acid sequence(s) into a plantof lettuce variety 79-504 RZ (or cells thereof), and exemplify someexogenous nucleic acid sequence(s) which may be introduced into a plantof lettuce variety 79-504 RZ (or cells thereof) of the invention, aswell as techniques, promoters, vectors etc., to thereby obtain furtherplants of lettuce variety 79-504 RZ, plant parts and cells, seeds, otherpropagation material harvestable parts of these plants, etc. of theinvention, e.g. tissue culture, including a cell or protoplast, such asan embryo, meristem, cotyledon, pollen, leaf, anther, root, root tip,pistil, flower, seed or stalk.

The invention further relates to propagation material for producingplants of the invention. Such propagation material may comprise interalia seeds of the claimed plant and parts of the plant that are involvedin sexual reproduction. Such parts are for example selected from thegroup consisting of seeds, microspores, pollen, ovaries, ovules, embryosacs and egg cells. In addition, the invention relates to propagationmaterial which may comprise parts of the plant that are suitable forvegetative reproduction, for example cuttings, roots, stems, cells,protoplasts.

According to a further aspect thereof the propagation material of theinvention may comprise a tissue culture of the claimed plant. The tissueculture may comprise regenerable cells. Such tissue culture may bederived from leaves, pollen, embryos, cotyledon, hypocotyls,meristematic cells, roots, root tips, anthers, flowers, seeds and stems.(See generally U.S. Pat. No. 7,041,876 on lettuce being recognized as aplant that may be regenerated from cultured cells or tissue).

Also, the invention comprehends methods for producing a seed of a 79-504RZ-derived lettuce plant which may comprise (a) crossing a plant oflettuce variety 79-504 RZ, representative seed of which having beendeposited under NCIMB Accession No. NCIMB 42166, with a second lettuceplant, and (b) whereby seed of a 79-504 RZ-derived lettuce plant form.Such a method may further comprise (c) crossing a plant grown from79-504 RZ-derived lettuce seed with itself or with a second lettuceplant to yield additional 79-504 RZ-derived lettuce seed, (d) growingthe additional 79-504 RZ-derived lettuce seed of step (c) to yieldadditional 79-504 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to further generate 79-504 RZ-derived lettuce plants.

The invention further relates to the above methods that may furthercomprise selecting at steps b), d), and e), a 79-504 RZ-derived lettuceplant, exhibiting a combination of traits including resistance againstdowny mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

In particular, the invention relates to methods for producing a seed ofa 79-504 RZ-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 79-504 RZ, representative seed of which havingbeen deposited under NCIMB Accession No. NCIMB 42166, with a secondlettuce plant and (b) whereby seed of a 79-504 RZ-derived lettuce plantforms, wherein such a method may further comprise (c) crossing a plantgrown from 79-504 RZ-derived lettuce seed with itself or with a secondlettuce plant to yield additional 79-504 RZ-derived lettuce seed, (d)growing the additional 79-504 RZ-derived lettuce seed of step (c) toyield additional 79-504 RZ-derived lettuce plants and selecting for aplant exhibiting a combination of traits includingresistance againstdowny mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate, and (e)repeating the crossing and growing of steps (c) and (d) for anadditional 3-10 generations to further generate 79-504 RZ-derivedlettuce plants that exhibit a combination of traits including resistanceagainst downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremialactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,and lettuce mosaic virus (LMV), as well as an extraordinary high numberof substantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.

The invention additionally provides a method of introducing a desiredtrait into a plant of lettuce variety 79-504 RZ which may comprise: (a)crossing a plant of lettuce variety 79-504 RZ, representative seed ofwhich having been deposited under NCIMB Accession No. NCIMB 42166, witha second lettuce plant that may comprise a desired trait to produce F1progeny; (b) selecting an F1 progeny that may comprise the desiredtrait; (c) crossing the selected F1 progeny with a plant of lettucevariety 79-504 RZ, to produce backcross progeny; (d) selecting backcrossprogeny which may comprise the desired trait and the physiological andmorphological characteristic of a plant of lettuce variety 79-504 RZ;and, optionally, (e) repeating steps (c) and (d) one or more times insuccession to produce selected fourth or higher backcross progeny thatmay comprise the desired trait and all of the physiological andmorphological characteristics of a plant of lettuce variety 79-504 RZ,when grown in the same environmental conditions. The invention, ofcourse, includes a lettuce plant produced by this method.

Backcrossing may also be used to improve an inbred plant. Backcrossingtransfers a specific desirable trait from one inbred or non-inbredsource to an inbred that lacks that trait. This may be accomplished, forexample, by first crossing a superior inbred (A) (recurrent parent) to adonor inbred (non-recurrent parent), which carries the appropriate locusor loci for the trait in question. The progeny of this cross are thenmated back to the superior recurrent parent (A) followed by selection inthe resultant progeny for the desired trait to be transferred from thenon-recurrent parent. After five or more backcross generations withselection for the desired trait, the progeny are heterozygous for locicontrolling the characteristic being transferred, but are like thesuperior parent for most or almost all other loci. The last backcrossgeneration would be selfed to give pure breeding progeny for the traitbeing transferred. When a plant of lettuce variety 79-504 RZ,representative seed of which having been deposited under NCIMB AccessionNo. NCIMB 42166, is used in backcrossing, offspring retaining thecombination of traits including resistance against downy mildew strainsBl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate are progeny within the ambit of the invention.Backcrossing methods may be used with the present invention to improveor introduce a characteristic into a plant of the invention, being aplant of lettuce variety 79-504 RZ. See, e.g., Pat. No. 7,705,206(incorporated herein by reference consistent with the aboveINCORPORATION BY REFERENCE section), for a general discussion relatingto backcrossing.

The invention further involves a method of determining the genotype of aplant of lettuce variety 79-504 RZ, representative seed of which hasbeen deposited under NCIMB Accession No. NCIMB 42166, or a firstgeneration progeny thereof, which may comprise obtaining a sample ofnucleic acids from said plant and detecting in said nucleic acids aplurality of polymorphisms. This method may additionally comprise thestep of storing the results of detecting the plurality of polymorphismson a computer readable medium. The plurality of polymorphisms areindicative of and/or give rise to the expression of the morphologicaland physiological characteristics of lettuce variety 79-504 RZ.

There are various ways of obtaining genotype data from a nucleic acidsample. Genotype data may be gathered which is specific for certainphenotypic traits (e.g. gene sequences), but also patterns of randomgenetic variation may be obtained to construct a so-called DNAfingerprint. Depending on the technique used a fingerprint may beobtained that is unique for lettuce variety 79-504 RZ. Obtaining aunique DNA fingerprint depends on the genetic variation present in avariety and the sensitivity of the fingerprinting technique. A techniqueknown in the art to provide a good fingerprint profile is called AFLPfingerprinting technique (See generally U.S. Pat. No. 5,874,215), butthere are many other marker based techniques, such as RFLP (orRestriction fragment length polymorphism), SSLP (or Simple sequencelength polymorphism), RAPD (or Random amplification of polymorphic DNA)VNTR (or Variable number tandem repeat), Microsatellite polymorphism,SSR (or Simple sequence repeat), STR (or Short tandem repeat), SFP (orSingle feature polymorphism) DArT (or Diversity Arrays Technology), RADmarkers (or Restriction site associated DNA markers) (e.g. Baird et al.PloS One Vol. 3 e3376, 2008; Semagn et al. African Journal ofBiotechnology Vol. 5 number 25 pp. 2540-2568, 29 Dec., 2006). Nowadays,sequence-based methods are utilizing Single Nucleotide Polymorphisms(SNPs) that are randomly distributed across genomes, as a common toolfor genotyping (e.g. Elshire et al. PloS One Vol. 6: e19379, 2011;Poland et al. PloS One Vol. 7: e32253; Truong et al. PLoS One Vol. 7number 5: e37565, 2012).

With any of the aforementioned genotyping techniques, polymorphisms maybe detected when the genotype and/or sequence of the plant of interestis compared to the genotype and/or sequence of one or more referenceplants. As used herein, the genotype and/or sequence of a referenceplant may be derived from, but is not limited to, any one of thefollowing: parental lines, closely related plant varieties or species,complete genome sequence of a related plant variety or species, or thede novo assembled genome sequence of one or more related plant varietiesor species. For example, it is possible to detect polymorphisms for thecharacteristic of Bremia resistance by comparing the genotype and/or thesequence of lettuce variety 79-504 RZ with the genotype and/or thesequence of one or more reference plants. The reference plant(s) usedfor comparison in this example may for example be, but is not limitedto, any of the comparison varieties Emerson, Aquino, Pascal, Socrates,or Grand rapids. It is also possible for example, to detectpolymorphisms for the multileaf character by comparing the genotypeand/or the sequence of lettuce variety 79-504 RZ with the genotypeand/or the sequence of one or more reference plants. The referenceplant(s) used for comparison may for example be, but is not limited to,any of the comparison varieties Emerson, Aquino, Pascal, Socrates, orGrand rapids.

The polymorphism revealed by these techniques may be used to establishlinks between genotype and phenotype. The polymorphisms may thus be usedto predict or identify certain phenotypic characteristics, individuals,or even species. The polymorphisms are generally called markers. It iscommon practice for the skilled artisan to apply molecular DNAtechniques for generating polymorphisms and creating markers.

The polymorphisms of this invention may be provided in a variety ofmediums to facilitate use, e.g. a database or computer readable medium,which may also contain descriptive annotations in a form that allows askilled artisan to examine or query the polymorphisms and obtain usefulinformation.

As used herein “database” refers to any representation of retrievablecollected data including computer files such as text files, databasefiles, spreadsheet files and image files, printed tabulations andgraphical representations and combinations of digital and image datacollections. In a preferred aspect of the invention, “database” refersto a memory system that may store computer searchable information.

As used herein, “computer readable media” refers to any medium that maybe read and accessed directly by a computer. Such media include, but arenot limited to: magnetic storage media, such as floppy discs, hard disc,storage medium and magnetic tape; optical storage media such as CD-ROM;electrical storage media such as RAM, DRAM, SRAM, SDRAM, ROM; and PROMs(EPROM, EEPROM, Flash EPROM), and hybrids of these categories such asmagnetic/optical storage media. A skilled artisan may readily appreciatehow any of the presently known computer readable mediums may be used tocreate a manufacture which may comprise computer readable medium havingrecorded thereon a polymorphism of the present invention.

As used herein, “recorded” refers to the result of a process for storinginformation in a retrievable database or computer readable medium. Forinstance, a skilled artisan may readily adopt any of the presently knownmethods for recording information on computer readable medium togenerate media which may comprise the polymorphisms of the presentinvention. A variety of data storage structures are available to askilled artisan for creating a computer readable medium where the choiceof the data storage structure will generally be based on the meanschosen to access the stored information. In addition, a variety of dataprocessor programs and formats may be used to store the polymorphisms ofthe present invention on computer readable medium.

The present invention further provides systems, particularlycomputer-based systems, which contain the polymorphisms describedherein. Such systems are designed to identify the polymorphisms of thisinvention. As used herein, “a computer-based system” refers to thehardware, software and memory used to analyze the polymorphisms. Askilled artisan may readily appreciate that any one of the currentlyavailable computer-based system are suitable for use in the presentinvention.

Lettuce leaves are sold in packaged form, including without limitationas pre-packaged lettuce salad or as lettuce heads. Mention is made ofU.S. Pat. No. 5,523,136, incorporated herein by reference consistentwith the above INCORPORATION BY REFERENCE section, which providespackaging film, and packages from such packaging film, including suchpackaging containing leafy produce, and methods for making and usingsuch packaging film and packages, which are suitable for use with thelettuce leaves of the invention. Thus, the invention comprehends the useof and methods for making and using the leaves of the lettuce plant ofthe invention, as well as leaves of lettuce plants derived from theinvention. The invention further relates to a container which maycomprise one or more plants of the invention, or one or more lettuceplants derived from a plant of the invention, in a growth substrate forharvest of leaves from the plant in a domestic environment. This way theconsumer may pick very fresh leaves for use in salads. More generally,the invention includes one or more plants of the invention or one ormore plants derived from lettuce of the invention, wherein the plant isin a ready-to-harvest condition, including with the consumer picking hisown, and further including a container which may comprise one or more ofthese plants.

Having thus described in detail preferred embodiments of the presentinvention, it is to be understood that the invention is not to belimited to particular details set forth in the above description as manyapparent variations thereof are possible without departing from thespirit or scope of the present invention.

The invention is further described by the following numbered paragraphs:

-   -   1. A lettuce plant designated 79-504 RZ, representative seed of        which having been deposited under NCIMB Accession No. 42166,        wherein said plant comprises at least the following combination        of traits including resistance against downy mildew strains Bl:1        to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce        aphid (Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic        virus (LMV), as well as an extraordinary high number of        substantially equally sized leaves, which leaves are medium        green, slightly to moderately blistered, and have a slightly to        moderately undulated apical leaf margin, which is shallowly        dentate.    -   2. The lettuce plant of paragraph 1 wherein the plant is very        slow bolting.    -   3. A seed of the plant of paragraph 1.    -   4. Parts of the plant of paragraph 1, wherein said parts of the        plant are suitable for sexual reproduction.    -   5. Parts of the plant of paragraph 4, wherein said parts are        selected from the group consisting of microspores, pollen,        ovaries, ovules, embryo sacs and egg cells.    -   6. Parts of the plant of paragraph 1, wherein said parts of the        plant are suitable for vegetative reproduction.    -   7. Parts as of paragraph 6, wherein said parts are selected from        the group consisting of cuttings, roots, stems, cells and        protoplasts.    -   8. A tissue culture of regenerable cells from the lettuce plant        of paragraph 1.    -   9. The tissue culture of paragraph 8, wherein said cells or        protoplasts of the tissue culture are derived from a tissue        selected from the group consisting of leaves, pollen, embryos,        cotyledon, hypocotyls, meristematic cells, roots, root tips,        anthers, flowers, seeds and stems.    -   10. A method for producing a progeny plant of a lettuce plant of        paragraph 1, comprising crossing the plant of paragraph 1 with        itself or with another lettuce plant, harvesting the resultant        seed, and growing said seed.    -   11. A progeny plant produced by the method of paragraph 10,        wherein said progeny plant exhibits a combination of traits        including resistance against downy mildew strains Bl:1 to Bl:31,        CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid        (Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus        (LMV), as well as an extraordinary high number of substantially        equally sized leaves, which leaves are medium green, slightly to        moderately blistered, and have a slightly to moderately        undulated apical leaf margin, which is shallowly dentate.    -   12. A progeny plant produced by the method of paragraph 10,        wherein said progeny plant has all the morphological and        physiological characteristics of the lettuce plant designated        79-504 RZ, representative seed of which having been deposited        under NCIMB Accession No. 42166, wherein said plant comprises at        least the following combination of traits resistance against        downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia        lactucae), currant-lettuce aphid (Nasonovia ribisnigri) biotype        Nr:0, and lettuce mosaic virus (LMV), as well as an        extraordinary high number of substantially equally sized leaves,        which leaves are medium green, slightly to moderately blistered,        and have a slightly to moderately undulated apical leaf margin,        which is shallowly dentate.    -   13. A progeny plant produced by the method of paragraph 10,        wherein said progeny plant, representative seed of which having        been deposited under NCIMB Accession 42166, is modified in one        or more other characteristics.    -   14. The progeny plant of paragraph 13, wherein the modification        is effected by mutagenesis.    -   15. The progeny plant of paragraph 13, wherein the modification        is effected by transformation with a transgene.    -   16. A method of producing a hybrid lettuce seed comprising        crossing a first parent lettuce plant with a second parent        lettuce plant and harvesting the resultant hybrid lettuce seed,        wherein said first parent lettuce plant or said second parent        lettuce plant is the lettuce plant of paragraph 1.    -   17. A hybrid lettuce plant produced by the method of paragraph        16.    -   18. A method of producing a lettuce cultivar exhibiting a        combination of traits including resistance against downy mildew        strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),        currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and        lettuce mosaic virus (LMV), as well as an extraordinary high        number of substantially equally sized leaves, which leaves are        medium green, slightly to moderately blistered, and have a        slightly to moderately undulated apical leaf margin, which is        shallowly dentate, comprising: crossing a mother lettuce plant        with a father lettuce plant to produce a hybrid seed; growing        said hybrid seed to produce a hybrid plant; selfing said hybrid        plant to produce F2 progeny seed; growing said F2 progeny seed        to produce F2-plants; selecting said F2-plants for exhibiting        resistance against downy mildew strains Bl:1 to Bl:31, CA-I to        CA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonovia        ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), as        well as an extraordinary high number of substantially equally        sized leaves, which leaves are medium green, slightly to        moderately blistered, and have a slightly to moderately        undulated apical leaf margin, which is shallowly dentate, and,        selfing said selected F2-plants to produce F3 progeny seed;        growing said F3 progeny seed to produce F3-plants; selecting        F3-plants for exhibiting resistance against downy mildew strains        Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),        currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and        lettuce mosaic virus (LMV), as well as an extraordinary high        number of substantially equally sized leaves, which leaves are        medium green, slightly to moderately blistered, and have a        slightly to moderately undulated apical leaf margin, which is        shallowly dentate, optionally followed by more selfing and        selection steps.    -   19. A lettuce cultivar produced by the method of paragraph 18.    -   20. A method for producing lettuce leaves as a fresh vegetable        comprising packaging leaves of a plant of paragraph 1.    -   21. A method for producing lettuce leaves as a processed food        comprising processing leaves of a plant of paragraph 1.    -   22. One or more lettuce plants of paragraph 1, in a container,        for harvest of leaves.    -   23. A lettuce plant having morphological and/or physiological        characteristics of a lettuce plant, representative seed of which        having been deposited under NCIMB Accession No. 42166.    -   24. A method of introducing a desired trait into a plant of        lettuce variety 79-504 RZ comprising: (a) crossing a plant of        lettuce variety 79-504 RZ, representative seed of which having        been deposited under NCIMB Accession No. NCIMB 42166, with a        second lettuce plant that comprises the desired trait to produce        F1 progeny; (b) selecting an F1 progeny that comprises the        desired trait; (c) crossing the selected F1 progeny with a plant        of lettuce variety 79-504 RZ, to produce backcross progeny        and (d) selecting backcross progeny comprising the desired trait        and the physiological and morphological characteristic of a        plant of lettuce variety 79-504 RZ, when grown in the same        environmental conditions.    -   25. The method of paragraph 24 further comprising (e) repeating        steps (c) and (d) one or more times in succession to produce        selected fourth or higher backcross progeny that comprise the        desired trait and all of the physiological and morphological        characteristics of a plant of lettuce variety 79-504 RZ, when        grown in the same environmental conditions.    -   26. A lettuce plant produced by the method of paragraph 24 or        25.    -   27. A method for producing a seed of a 79-504 RZ-derived lettuce        plant comprising (a) crossing a plant of lettuce variety 79-504        RZ, representative seed of which having been deposited under        NCIMB Accession No. NCIMB 42166, with a second lettuce plant,        and (b) whereby seed of a 79-504 RZ-derived lettuce plant form.    -   28. The method of paragraph 27 further comprising (c) crossing a        plant grown from 79-504 RZ-derived lettuce seed with itself or        with a second lettuce plant to yield additional 79-504        RZ-derived lettuce seed, (d) growing the additional 79-504        RZ-derived lettuce seed of step (c) to yield additional 79-504        RZ-derived lettuce plants, and (e) repeating the crossing and        growing of steps (c) and (d) for an additional 3-10 generations        to generate further 79-504 RZ-derived lettuce plants.    -   29. The method of paragraph 27 or 28 further comprising        selecting at steps b), d), and e), a 79-504 RZ-derived lettuce        plant, exhibiting a combination of traits including resistance        against downy mildew strains Bl:1 to Bl:31, CA-I to CA-VIII        (Bremia lactucae), currant-lettuce aphid (Nasonovia ribisnigri)        biotype Nr:0, and lettuce mosaic virus (LMV), as well as an        extraordinary high number of substantially equally sized leaves,        which leaves are medium green, slightly to moderately blistered,        and have a slightly to moderately undulated apical leaf margin,        which is shallowly dentate.    -   30. A seed produced by the method of paragraphs 27, 28, or 29.    -   31. A method of determining the genotype of a plant of lettuce        variety 79-504 RZ, representative seed of which has been        deposited under NCIMB Accession No. NCIMB 42166, or a first        generation progeny thereof, comprising obtaining a sample of        nucleic acids from said plant and comparing said nucleic acids        to a sample of nucleic acids obtained from a reference plant,        and detecting a plurality of polymorphisms between the two        nucleic acid samples, wherein the plurality of polymorphisms are        indicative of lettuce variety 79-504 RZ and/or give rise to the        expression of any one or more, or all, of the morphological and        physiological characteristics of lettuce variety 79-504 RZ of        paragraph 1.    -   32. The method of paragraph 31 additionally comprising the step        of storing the results of detecting the plurality of        polymorphisms on a computer readable medium, or transmitting the        results of detecting the plurality of polymorphisms.    -   33. The computer readable medium of paragraph 32.    -   34. Progeny of lettuce variety 79-504 RZ obtained by further        breeding with said variety.    -   35. The method of claim 28 further comprising selecting at steps        b), d), and e), a 79-504 RZ-derived lettuce plant, exhibiting        one or more of the following traits resistance against downy        mildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),        currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and        lettuce mosaic virus (LMV), as well as an extraordinary high        number of substantially equally sized leaves, which leaves are        medium green, slightly to moderately blistered, and have a        slightly to moderately undulated apical leaf margin, which is        shallowly dentate.

What is claimed is:
 1. A lettuce plant designated 79-504 RZ,representative seed of which having been deposited under NCIMB AccessionNo. 42166, wherein said plant comprises at least the followingcombination of traits including resistance against downy mildew strainsBl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate.
 2. The lettuce plant of claim 1 wherein the plant isvery slow bolting.
 3. A seed of the plant of claim
 1. 4. Parts of theplant of claim 1, wherein said parts of the plant are suitable forsexual reproduction.
 5. Parts of the plant as claimed in claim 4,wherein said parts are selected from the group consisting ofmicrospores, pollen, ovaries, ovules, embryo sacs and egg cells. 6.Parts of the plant of claim 1, wherein said parts of the plant aresuitable for vegetative reproduction.
 7. Parts as claimed in claim 6,wherein said parts are selected from the group consisting of cuttings,roots, stems, cells and protoplasts.
 8. A tissue culture of regenerablecells from the lettuce plant of claim
 1. 9. The tissue culture asclaimed in claim 8, wherein said cells or protoplasts of the tissueculture are derived from a tissue selected from the group consisting ofleaves, pollen, embryos, cotyledon, hypocotyls, meristematic cells,roots, root tips, anthers, flowers, seeds and stems.
 10. A method forproducing a progeny plant of a lettuce plant of claim 1, comprisingcrossing the plant of claim 1 with itself or with another lettuce plant,harvesting the resultant seed, and growing said seed.
 11. A progenyplant produced by the method of claim 10, wherein said progeny plantexhibits a combination of traits including resistance against downymildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.
 12. A progenyplant produced by the method of claim 10, wherein said progeny plant hasall the morphological and physiological characteristics of the lettuceplant designated 79-504 RZ, representative seed of which having beendeposited under NCIMB Accession No. 42166, wherein said plant comprisesat least the following combination of traits resistance against downymildew strains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate.
 13. A progenyplant produced by the method of claim 10, wherein said progeny plant,representative seed of which having been deposited under NCIMB Accession42166, is modified in one or more other characteristics.
 14. The progenyplant as claimed in claim 13, wherein the modification is effected bymutagenesis.
 15. The progeny plant as claimed in claim 13, wherein themodification is effected by transformation with a transgene.
 16. Amethod of producing a hybrid lettuce seed comprising crossing a firstparent lettuce plant with a second parent lettuce plant and harvestingthe resultant hybrid lettuce seed, wherein said first parent lettuceplant or said second parent lettuce plant is the lettuce plant ofclaim
 1. 17. A hybrid lettuce plant produced by the method of claim 16.18. A method of producing a lettuce cultivar exhibiting a combination oftraits including resistance against downy mildew strains Bl:1 to Bl:31,CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid (Nasonoviaribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), as well as anextraordinary high number of substantially equally sized leaves, whichleaves are medium green, slightly to moderately blistered, and have aslightly to moderately undulated apical leaf margin, which is shallowlydentate, comprising: crossing a mother lettuce plant with a fatherlettuce plant to produce a hybrid seed; growing said hybrid seed toproduce a hybrid plant; selfing said hybrid plant to produce F2 progenyseed; growing said F2 progeny seed to produce F2-plants; selecting saidF2-plants for exhibiting resistance against downy mildew strains Bl:1 toBl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate, and, selfing said selected F2-plants to produce F3progeny seed; growing said F3 progeny seed to produce F3-plants;selecting F3-plants for exhibiting resistance against downy mildewstrains Bl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae),currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, and lettucemosaic virus (LMV), as well as an extraordinary high number ofsubstantially equally sized leaves, which leaves are medium green,slightly to moderately blistered, and have a slightly to moderatelyundulated apical leaf margin, which is shallowly dentate, optionallyfollowed by more selfing and selection steps.
 19. A lettuce cultivarproduced by the method of claim
 18. 20. A method for producing lettuceleaves as a fresh vegetable comprising packaging leaves of a plant ofclaim
 1. 21. A method for producing lettuce leaves as a processed foodcomprising processing leaves of a plant of claim
 1. 22. A containercomprising one or more lettuce plants of claim 1 for harvesting leaves.23. A lettuce plant having morphological and/or physiologicalcharacteristics of a lettuce plant, representative seed of which havingbeen deposited under NCIMB Accession No.
 42166. 24. A method ofintroducing a desired trait into a plant of lettuce variety 79-504 RZcomprising: (a) crossing a plant of lettuce variety 79-504 RZ,representative seed of which having been deposited under NCIMB AccessionNo. NCIMB 42166, with a second lettuce plant that comprises the desiredtrait to produce F1 progeny; (b) selecting an F1 progeny that comprisesthe desired trait; (c) crossing the selected F1 progeny with a plant oflettuce variety 79-504 RZ, to produce backcross progeny and (d)selecting backcross progeny comprising the desired trait and thephysiological and morphological characteristic of a plant of lettucevariety 79-504 RZ, when grown in the same environmental conditions. 25.The method of claim 24 further comprising (e) repeating steps (c) and(d) one or more times in succession to produce selected fourth or higherbackcross progeny that comprise the desired trait and all of thephysiological and morphological characteristics of a plant of lettucevariety 79-504 RZ, when grown in the same environmental conditions. 26.A lettuce plant produced by the method of claim
 24. 27. A method forproducing a seed of a 79-504 RZ-derived lettuce plant comprising (a)crossing a plant of lettuce variety 79-504 RZ, representative seed ofwhich having been deposited under NCIMB Accession No. NCIMB 42166, witha second lettuce plant, and (b) whereby seed of a 79-504 RZ-derivedlettuce plant form.
 28. The method of claim 27 further comprising (c)crossing a plant grown from 79-504 RZ-derived lettuce seed with itselfor with a second lettuce plant to yield additional 79-504 RZ-derivedlettuce seed, (d) growing the additional 79-504 RZ-derived lettuce seedof step (c) to yield additional 79-504 RZ-derived lettuce plants, and(e) repeating the crossing and growing of steps (c) and (d) for anadditional 3-10 generations to generate further 79-504 RZ-derivedlettuce plants.
 29. The method of claim 28 further comprising selectingat steps b), d), and e), a 79-504 RZ-derived lettuce plant, exhibiting acombination of traits including resistance against downy mildew strainsBl:1 to Bl:31, CA-I to CA-VIII (Bremia lactucae), currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, and lettuce mosaic virus (LMV), aswell as an extraordinary high number of substantially equally sizedleaves, which leaves are medium green, slightly to moderately blistered,and have a slightly to moderately undulated apical leaf margin, which isshallowly dentate.
 30. A seed produced by the method of claim
 27. 31. Amethod of determining the genotype of a plant of lettuce variety 79-504RZ, representative seed of which has been deposited under NCIMBAccession No. NCIMB 42166, or a first generation progeny thereof,comprising obtaining a sample of nucleic acids from said plant andcomparing said nucleic acids to a sample of nucleic acids obtained froma reference plant, and detecting a plurality of polymorphisms betweenthe two nucleic acid samples, wherein the plurality of polymorphisms areindicative of lettuce variety 79-504 RZ and/or give rise to theexpression of any one or more, or all, of the morphological andphysiological characteristics of lettuce variety 79-504 RZ as claimed inclaim
 1. 32. The method of claim 31 additionally comprising the step ofstoring the results of detecting the plurality of polymorphisms on acomputer readable medium, or transmitting the results of detecting theplurality of polymorphisms.
 33. The computer readable medium of claim32.
 34. Progeny of lettuce variety 79-504 RZ obtained by furtherbreeding with said variety.